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.TH STRTOUL 3C "Nov 1, 2003"
.SH NAME
strtoul, strtoull \- convert string to unsigned long
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBunsigned long\fR \fBstrtoul\fR(\fBconst char *restrict\fR \fIstr\fR,
     \fBchar **restrict\fR \fIendptr\fR, \fBint\fR \fIbase\fR);
.fi

.LP
.nf
\fBunsigned long long\fR \fBstrtoull\fR(\fBconst char *restrict\fR \fIstr\fR,
     \fBchar **restrict\fR \fIendptr\fR, \fBint\fR \fIbase\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBstrtoul()\fR function converts the initial portion of the string pointed
to by \fIstr\fR to a type \fBunsigned long int\fR representation. First it
decomposes the input string into three parts: an initial, possibly empty,
sequence of white-space characters (as specified by \fBisspace\fR(3C)); a
subject sequence interpreted as an integer represented in some radix determined
by the value of \fIbase\fR; and a final string of one or more unrecognised
characters, including the terminating null byte of the input string. Then it
attempts to convert the subject sequence to an unsigned integer, and returns
the result.
.sp
.LP
If the value of \fIbase\fR is 0, the expected form of the subject sequence is
that of a decimal constant, octal constant or hexadecimal constant, any of
which may be preceded by a + or \(mi sign. A decimal constant begins with a
non-zero digit, and consists of a sequence of decimal digits. An octal constant
consists of the prefix 0 optionally followed by a sequence of the digits 0 to 7
only. A hexadecimal constant consists of the prefix 0x or 0X followed by a
sequence of the decimal digits and letters a (or A) to f (or F) with values 10
to 15 respectively.
.sp
.LP
If the value of \fIbase\fR is between 2 and 36, the expected form of the
subject sequence is a sequence of letters and digits representing an integer
with the radix specified by \fIbase\fR, optionally preceded by a + or \(mi
sign. The letters from a (or A) to z (or Z) inclusive are ascribed the values
10 to 35; only letters whose ascribed values are less than that of \fIbase\fR
are permitted. If the value of \fIbase\fR is 16, the characters 0x or 0X may
optionally precede the sequence of letters and digits, following the sign if
present.
.sp
.LP
The subject sequence is defined as the longest initial subsequence of the input
string, starting with the first non-white-space character, that is of the
expected form. The subject sequence contains no characters if the input string
is empty or consists entirely of white-space characters, or if the first
non-white-space character is other than a sign or a permissible letter or
digit.
.sp
.LP
If the subject sequence has the expected form and the value of \fIbase\fR is 0,
the sequence of characters starting with the first digit is interpreted as an
integer constant. If the subject sequence has the expected form and the value
of \fIbase\fR is between 2 and 36, it is used as the base for conversion,
ascribing to each letter its value as given above. If the subject sequence
begins with a minus sign, the value resulting from the conversion is negated. A
pointer to the final string is stored in the object pointed to by \fIendptr\fR,
provided that \fIendptr\fR is not a null pointer.
.sp
.LP
In other than the POSIX locale, additional implementation-dependent subject
sequence forms may be accepted.
.sp
.LP
If the subject sequence is empty or does not have the expected form, no
conversion is performed; the value of \fIstr\fR is stored in the object pointed
to by \fIendptr\fR, provided that \fIendptr\fR is not a null pointer.
.sp
.LP
The \fBstrtoull()\fR function is identical to \fBstrtoul()\fR except that it
returns the value represented by \fIstr\fR as an \fBunsigned long long\fR.
.SH RETURN VALUES
.sp
.LP
Upon successful completion \fBstrtoul()\fR returns the converted value, if any.
If no conversion could be performed, \fB0\fR is returned and \fBerrno\fR may be
set to \fBEINVAL\fR. If the correct value is outside the range of representable
values, \fBULONG_MAX\fR is returned and \fBerrno\fR is set to \fBERANGE\fR.
.SH ERRORS
.sp
.LP
The \fBstrtoul()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fIbase\fR is not supported.
.RE

.sp
.ne 2
.na
\fB\fBERANGE\fR\fR
.ad
.RS 10n
The value to be returned is not representable.
.RE

.sp
.LP
The \fBstrtoul()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
No conversion could be performed.
.RE

.SH USAGE
.sp
.LP
Because 0 and \fBULONG_MAX\fR are returned on error and are also valid returns
on success, an application wishing to check for error situations should set
\fBerrno\fR to 0, then call \fBstrtoul()\fR, then check \fBerrno\fR and if it
is non-zero, assume an error has occurred.
.sp
.LP
Unlike \fBstrtod\fR(3C) and \fBstrtol\fR(3C), \fBstrtoul()\fR must always
return a non-negative number; so, using the return value of \fBstrtoul()\fR for
out-of-range numbers with \fBstrtoul()\fR could cause more severe problems than
just loss of precision if those numbers can ever be negative.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR isalpha (3C),
.BR isspace (3C),
.BR scanf (3C),
.BR strtod (3C),
.BR strtol (3C),
.BR attributes (7),
.BR standards (7)
